This invention relates to a control unit for switching on and off and controlling household appliances, specifically large household appliances such as kitchen ranges (stoves), dishwashers, washing machines, and similar devices. More particularly the invention relates to such a control unit having a control surface without perforations formed by a plate that is stable in form, and a pressure-sensitive signal generator to which a processor is attached for processing electrical signals generated. The invention also relates to a process for switching and controlling household appliances that involves a pressure-sensitive signal generator generating electrical signals that are sent to a processor for analyzing pressure exerted on a control surface for selecting a function.
German patent document (DE 39 20 257 A1) discloses a control unit (control panel) having control elements, with corresponding display elements. Since control buttons are used, an operational area of a control surface is perforated and difficult to clean.
German patent document (DE 42 29 731 A1) discloses a control panel which is included in a built-in housing with a cover plate. In this design, the display and/or control elements of the control panel are arranged on the inside of the cover plate. A household appliance can also be switched and controlled via remote infrared control. Also here buttons are used as control elements.
German patent document (DE 44 07 741 A1) discloses a sensor switching device. In addition to control buttons for switching an appliance on or off a microprocessor is included for switching on or off a power control device, such as a heating element on a cook top of a range, for example. For safety reasons, two control buttons must be pressed in a time sequence for switching the power control device on.
U.S. patent document (U.S. Pat. No. 4,190,785) discloses a pressure-sensitive signal generator. A piezoelectric layer is sandwiched between an electrically conductive substrate, or support material, and electrodes. The piezoelectric layer is present across an entire lower surface of the substrate. Action, or push, points in the form of pads are located on the substrate at specified positions, with an electrode located under the piezoelectric layer corresponding to each action point. When pressure is applied to a pad, an output voltage between the substrate and the respective electrode is modified. When this is done, an output voltage is defined for each pad such that a location where pressure is applied is determined in a signal processor by means of a nominal/actual comparison. An application of pressure beside the pads creates conditions that are indefinable for the signal processor, and operator errors may occur.
It is an object of this invention to provide a control unit for switching and controlling a household appliance in which an operational area of a control surface is not perforated, and, regarding its manipulation positions can be readily adapted to suit requirements of various appliances, and which reduces operator error.